FIGS. 3A and 3B show a cross-sectional view of a load locked vertical type heat treatment apparatus. As shown in FIGS. 3A and 3B, the load locked vertical type heat treatment apparatus is comprised of a treatment chamber 1 and an elevator chamber 11.
A reaction tube 2 is provided in the treatment chamber 1, and a compartment tube 3 is provided in the reaction tube 2. A manifold 4 is arranged below the treatment chamber 1 and has a gas inlet 9 for introducing a gas therein and a gas outlet 10 for exhausting the gas therefrom. A heater is positioned around the reaction tube 2 so that the reaction tube 2, objects 7 inside the reaction tube and the like can be heated.
A boat 5 for carrying a plurality of objects 7, such as semiconductor wafers, and a boat table 6 for supporting the boat 5 thereon can be moved in and out from the compartment tube 3 through the manifold 4. The objects 7 are carried by the boat 5 at vertical intervals. A treatment to be performed of the objects 7 may be to form a thin film by a chemical vapor deposition, annealing or the like.
The elevator chamber 11 is connected below the treatment chamber 1 through the manifold 4. The elevator chamber 11 is communicated with the treatment chamber 1 through an opening 11a provided at the top of the elevator chamber 11 and an opening 4a of the manifold 4 which has a diameter smaller than the opening 11a (see FIG. 3B). In the elevator chamber 11, untreated objects are placed on the boat 5, or treated objects are removed from the boat 5.
A sealing flange 8 having an outer diameter larger than the opening 4a and an inner diameter smaller than the opening 11a is mounted on the bottom surface of the boat table 6. The sealing flange 8 contacts a shoulder formed between the opening 4a and the opening 11a to open and close an interior space of the treatment chamber 1. By such opening and closing, the treatment chamber 1 is completely separated from an interior space of the elevator chamber 11.
The sealing flange 8 is mounted on one end of a movable member 12 which extends horizontally and has a hole provided at the other end. A feed screw 13 is screwed into the hole and extends upwardly and downwardly therethrough. The upper end of the feed screw 13 is rotatably mounted to an upper wall of the elevator chamber 11. The lower end of the screw 13 extends outside the elevator chamber 11 and passes through the bottom of the elevator chamber 11 via an O-ring (not shown) by which the interior of the elevator chamber 11 is maintained in vacuum.
A pulley 15b is mounted about the lower end of the feed screw 13 extending exterior to the elevator chamber 11. The pulley 15b is connected to a pulley 15a connected by a belt 16 to an end of a motor 14 provided exterior to a side wall of the elevator chamber 11. Thus, by driving the motor 14, rotation is transferred to the feed screw 13, and the movable member 12 travels upwardly and downwardly. Accordingly, the boat table 6 with the boat 5 mounted thereon is moved from the interior of the elevator chamber 11 into the treatment chamber 1, and vice versa. Whenever it is necessary to exhaust gas or vapor from the elevator chamber 11, the exhausting can be done through an outlet 17.
FIG. 3B shows the boat table 6 descended until the objects 7 are completely contained inside the elevator chamber 11. When placing objects 7 on the boat 5, the boat table 6 is descended into the elevator chamber 11 as shown in FIG. 3B and untreated objects are supplied to the boat 5 through an opening 20 and a gate valve 18. After treatment, in a similar manners the boat 5 is descended and treated objects are removed from the boat 5 and returned to a room 19.
However, in a load locked vertical type heat treatment apparatus of the art, means for elevating the boat table 6, that is the movable member 12, and the feed screw 13 are provided in the elevator chamber 11. Thus, particles or debris caused by rotating the feed screw 13 and screwing the feed screw 13 into the movable member 12 are present in the chamber 11.
Also, when evacuating the interior of the elevator chamber 11 and elevating the boat table 6, lubricating oil is required for the engaging section between the feed screw 13 and the boat table 6 in order to make the elevating motion smooth. The lubricating oil typically has a low vapor pressure, and when structures inside the elevator chamber 11 are heated by radiation from the heated objects 7 when the objects 7 are unloaded from the treatment chamber 1 after treatment, the lubricating oil is evaporated in the elevator chamber 11, thereby contaminating the objects 7.
Moreover, in a vacuum load locked apparatus, because an interior of a chamber is always in a state of vacuum, it is very difficult to provide a mechanism for rotating a boat table for supporting objects.
Accordingly, an objective of the present invention is to provide a load lock chamber for a vertical type heat treatment apparatus which has no elevating device requiring the provision of lubricating oil which is a source of particles causing contamination in the elevator chamber.
Another objective of the present invention is to provide a load lock chamber for a vertical type heat treatment apparatus which can rotate a boat table supporting objects from the exterior.